MAKSUTURVA PRESTASHOP PAYMENT GATEWAY MODULE rev. 121

Bugfixes:
- the module now supports Prestashop up to version 1.6.
- the module now removes quotation marks from product names and description – previously 
it caused errors in hash calculation
- product SKU is added when available, shipping method name used as shipping name when available
- Optional parameters (e.g. pre-selected payment method, buyer's identification code) are now included in the hash calculation when available (currently not available, though, but enabling is possible in further development - see _construct -method in MaksuturvaGatewayImplementation.php and Maksuturva Payment interface description).
- Module directory structure updated to enable installation through Prestashop user interface. 

Documentation updated.